When invoking the LoadDocumentResult method no results are returned.
This occurs when the export is done not to the Application Server, but to a file storage (FTP, SFTP, a local folder, etc).
From the LoadDocumentResult documentation:
This method can be used when exporting results to the ABBYY FlexiCapture database. When exporting to a file storage, null is returned
The Export Path in Export Settings should be set as a relative path:
And the Export Root Path property in the "Project Properties" -> "General" tab should be blank:
If there is an "Export root path" set then paths set in export settings will become relative to the root path, making the methods in question behave differently.